European air carriers are protesting against Brussels because of ghost flights, that is the routes that airlines are obliged to take, even with few passengers, in order to keep the take-off and landing slots in the European airports, as required by EU rules. For example, that the German Lufthansa would have operated 18 thousand "unnecessary" flights in Winter. The rule, in fact, provides for the reallocation of airline slots if they do not use them at least at 50% of their capacity. 

Some flights were operated with only the crew on board and no passengers. Otherwise airlines would lose their takeoff and landing rights at airports, as ruled by a law that came into effect in 1993. Due to the pandemic, Brussels lowered the slot occupancy rate in 2020 from 80 to 50 percent, but in July 2021 increased it again to 64 percent. 

Now the European Commissioner for Transport, Adina Valean, extended the deadline for restoring the 80% limit from March 27th to October 29th 2022. However, the choice does not shield Europe from fierce criticism. Both from some governments and environmentalists, who argue that ghost flights weaken the EU's commitment to cutting harmful gas emissions.